1. Field of the Invention
The present invention relates to a sound field correcting method of correcting a sound field characteristic in an audio system.
2. Description of the Related Art
The audio system is required to produce a sound field space that can give a presence. In the prior art, the sound field correcting method of the audio system disclosed in Utility Model Application Publication (KOKAI) Hei 6-13292 has been known.
In this audio system in the prior art, an equalizer for adjusting frequency characteristics of the input audio signals and delay circuits for delaying the audio signals output from the equalizer are provided, and then outputs of the delay circuits are supplied to loudspeakers.
Also, in order to correct the sound field characteristic, there are provided a pink noise generator, an impulse generator, a selector circuit, a microphone used to measure the reproduced sounds being reproduced by the loudspeakers, a frequency analyzing means, and a delay time calculating means. Then, a pink noise generated by the pink noise generator is supplied to the equalizer via the selector circuit, and an impulse signal generated by the impulse generator is directly supplied to the loudspeakers via the selector circuit.
Upon correcting the phase characteristic of the sound field space, propagation delay times of the impulse sounds from the loudspeakers to a listening position are measured by measuring the impulse sound reproduced via the loudspeakers by using the microphone while supplying directly the impulse signal from the above impulse generator to the loudspeakers, and then analyzing the measured signals by using the delay time calculating means.
In other words, the propagation delay times of respective impulse sounds are measured by directly supplying the impulse signal to the loudspeakers and calculating time differences from points of time when respective impulse signals are supplied to respective loudspeakers to points of time when respective impulse sounds being reproduced by every loudspeaker come up to the microphone by using the delay time calculating means. Thus, the phase characteristic of the sound field space can be corrected by adjusting the delay times of the delay circuits based on the measured propagation delay times.
Also, upon correcting the frequency characteristic of the sound field space, the pink noise is supplied from the pink noise generator to the equalizer and then the reproduced sounds of the pink noise being reproduced via the loudspeakers are measured by the microphone, and then frequency characteristics of these measured signals are analyzed by the frequency analyzing means. Thus, the frequency characteristic of the sound field space can be corrected by feedback-controlling the frequency characteristic of the equalizer based on the analyzed results.
However, in the audio system in the prior art, as described above, upon correcting the phase characteristic of the sound field space, the impulse signal is directly supplied to the loudspeakers. Therefore, there is such a subject that the phase characteristic of the overall audio system cannot be corrected into the phase characteristic that can produce the proper sound field space.
Also, upon correcting the frequency characteristic of the sound field space, a method of analyzing the frequency characteristics of the reproduced sounds of the pink noise by using a group of narrow-band filters and then feeding back the analyzed results to the equalizer is employed.
However, in case the frequency characteristics of measured signals derived from the reproduced sounds of the pink noise being reproduced via the loudspeakers are frequency-analyzed by individual narrow-band filters in a group of narrow-band filters, the analyzed result suitable for the frequency characteristic of the equalizer cannot be obtained with good precision. As a result, there is such a subject that, if the frequency characteristic of the equalizer is feedback-controlled based on the analyzed result, it becomes difficult to correct properly the frequency characteristic of the sound field space.